Since antigens released from tumor cells can thwart the host's immune reactivity against immunogenic tumors in favor of tumor growth, the present work proposes to develop an extracorporeal system to remove the tumor antigen as well as the bound antigen (antigen-antibody complex) from the patient's plasma and return his/her own purified plasma to the patient. The first phase of the proposed work involves in vitro studies on the efficiency of separation of tumor antigen from the plasma of a breast cancer patient and its effect on the lymphocyte cytotoxicity. The process of separation of tumor antigen from plasma involves three steps: (1) dissociation of immune complexes at pH 3.1; (2) separation of tumor antigen by ultrafiltration; and (3) readjustment of plasma pH by dialysis. In vitro studies are planned to design and develop this system to process the plasma from a cancer patient, and to determine the change in lymphocyte cytotoxicity due to the removal of tumor antigens from the plasma. (LB)